The present invention relates to a method for fabricating a semiconductor device, and more particularly, to a method for fabricating a semiconductor device using a multifunction hard mask (MFHM) layer.
As semiconductor devices become highly integrated, a micro sized pattern is fabricated and a photoresist layer becomes thinner in a mask process. As the photoresist layer becomes thinner, an etching margin is insufficient during an etching process and material formed at a lower portion of the photoresist layer is only partially etched, resulting in a reduction of a process margin. Such a reduction of the process margin may deteriorate characteristics of a semiconductor device. Currently, since the photoresist layer cannot ensure a sufficient process margin, the use of amorphous carbon as a hard mask has been suggested.
However, amorphous carbon may increase fabricating costs and make it difficult to perform the etching process. Further, in order to use the amorphous carbon as a hard mask, a silicon oxy-nitride (SiON) layer and an anti-reflective coating layer must be additionally formed before forming a photoresist layer.
An MFHM layer has been developed and employed as a substitute for amorphous carbon layer. The MFHM layer can be prepared in the form of a stack structure including a spin on carbon (SOC) layer and an MFHM layer. Since both the SOC layer and the MFHM layer can be formed through a coating process, the MFHM layer is advantageous in terms of the process margin and fabricating costs compared with the amorphous carbon.
However, when an over-etch is performed in an etch process in which the MFHM layer is etched using a fluorine-based gas, the SOC layer may be deformed by the fluorine-based gas.
FIGS. 1A and 1B are perspective views illustrating deformation of an SOC layer 11 due to a fluorine group.
If the fluorine group contacts the SOC layer 11 as shown in FIG. 1A, the SOC layer 11 may be deformed (11A) due to a stress in the layer (volume expansion) as shown in FIG. 1B.
FIG. 2 is a view illustrating a bond structure of an SOC layer and a fluorine group.
Referring to FIG. 2, as the fluorine group F consisting of large particles penetrates into the SOC layer in which hydrogen H consisting of small particles is bonded to carbon C consisting of large particles, the hydrogen H is replaced with the fluorine group F and then the fluorine group F reacts with the carbon C, so that the volume of the SOC layer increases.